Britain sweltered on its hottest April day in almost 70 years on Thursday with temperatures climbing above 29°C (84.2°F) in some areas, according to the Met Office.

Forecasters predict the nation will continue to bake over the weekend, but while many will welcome the sunshine, the hot weather has triggered warnings for London Marathon runners amid fears that Sunday’s race could be the warmest on record.

Warm weather

This Sunday’s London Marathon could be the warmest on record

Temperatures could hit 23°C (73.4°F) in the capital on Sunday when some 40,000 people will pound the city’s streets.

The Met Office’s predictions of “strong sunshine” and “very warm” weather has prompted marathon organisers to add more water, ice and shower stations to the 26.2-mile route.

Marathon runners told: go slower

Participants have been advised to consider dropping their target times and running more slowly.

And those planning to run in fancy dress have been urged to “think carefully” about whether it will be appropriate to do so in the conditions forecast.

Furry costume

Adam Smith, 45, who is attempting to set the record for fastest race dressed as a mythical creature, said: “My costume is particularly warm, with a nice and furry gnome hat and a toadstool to carry.

“My costume is particularly warm, with a furry gnome hat and toadstool”

“The plan is to go on as normal but I’ve asked if I can have short sleeves – I’m very conscious that there’s a world record and then there’s being safe.”

The hottest London Marathon on record was 22.7°C (72.9°F) in 1996, while the hottest April day ever in the UK was recorded in 1949 when the temperature reached 29.4°C (84.9°F) in Camden, north London.

Hot weather latest

The mercury soared on Thursday across England, Scotland, Wales and Northern Ireland, which all saw their warmest day of the year so far, the Met Office reported.

Temperatures reached 29.1°C (84.4℉) in St James’s Park, central London, while in Usk, in south-east Wales, it was not much cooler at 24°C (75.2℉).

At Fyvie Castle in Aberdeenshire a high of 21°C (69.8℉) was recorded and in Northern Ireland a high of 20°C (68℉) was reached.

The heat caused the cancellation of a horse race at Cheltenham but the races over shorter distances went ahead.

Experts have warned that pollen levels are high throughout much of the UK and said that conditions could be “uncomfortable” for hay fever sufferers.

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